The present invention refers to a anti-backlash device in a gear in which a toothed driving element is divided into two coaxial toothed members attached to one another by elastic means adapted to create a torque between these two coaxial toothed members.
Many solutions have already been proposed to eliminate backlash in a gear. For example, in the solution proposed in U.S. Pat. No. 4,660,432, a driving gear meshes with a driven gear fixed on a shaft and associated with two wheels arranged on both sides of the driving gear. The wheels are linked to the driving gear by prestressed elastic blocks ensuring an angular displacement between the driving gear and the two associated wheels. Such a device requires three wheels, and the presence of elastic blocks crossing two of the wheels does not allow using wheels or gears of small diameter, capable of transmitting a high torque, because the presence of holes weakens the board of the wheel, so that an adequate space has to be left between the edge of the holes and the bottom of the toothing. Due to this, the minimum diameter of the wheel is substantially increased.
Another anti-backlash device is described in U.S. Pat. No. 3,035,454, in which the elastic linking means between two coaxial wheels extend in the radial direction. Again, relatively large openings have to be recessed in one of the wheels to enable rods perpendicular to the board of one wheel to cross the other wheel so as to mesh with the radial elastic linking means, fixedly attached to the other wheel. These openings weaken the wheel and do not allow use of a wheel of small diameter. The length of the elastic linking arms is also limited by the radius of the wheel.
Another anti-backlash device is described in EP 1,034,923. It has similar features to the above mentioned solutions. In addition, this device does not allow adjusting the prestressing in accordance with the torque to be transmitted but allows only one determined stress.